(In reply to comment #2)
> Created an attachment (id=94092) [details]
> Patch
I moved the call to m_overflow.clear() to be outside the thumb check. It's possible for the thumb to be remove and the overflow not cleared.

Comment on attachment 94092[details]
Patch
View in context: https://bugs.webkit.org/attachment.cgi?id=94092&action=review
Test is (theoretically at least) flaky
> LayoutTests/fast/forms/slider-hit-testing.html:1
> +<head>
<!DOCTYPE html> plz unless this test needs quirks mode
> LayoutTests/fast/forms/slider-hit-testing.html:11
> +window.setTimeout(function() {
> + document.getElementById("slider").style.width = "100%";
> + changeAndCheckRangeValue();
> +}, 0);
the setTimeout is a bit odd - does the test not work if you run this code in an onload handler? technically speaking, this setTimeout _could_ execute immediately after parsing the end of the <script> and before the <input> is parsed, although in practice we'll nearly always parse through the end of this document before running timeouts.
> LayoutTests/fast/forms/slider-hit-testing.html:20
> + var x = slider.offsetLeft + (slider.clientWidth * .75);
> + var y = slider.offsetTop + (slider.clientHeight / 2);
could you add some comments indicating what you are trying to click on here and what should be happening?

Comment on attachment 94092[details]
Patch
View in context: https://bugs.webkit.org/attachment.cgi?id=94092&action=review>> LayoutTests/fast/forms/slider-hit-testing.html:1
>> +<head>
>
> <!DOCTYPE html> plz unless this test needs quirks mode
Done.
>> LayoutTests/fast/forms/slider-hit-testing.html:11
>> +}, 0);
>
> the setTimeout is a bit odd - does the test not work if you run this code in an onload handler? technically speaking, this setTimeout _could_ execute immediately after parsing the end of the <script> and before the <input> is parsed, although in practice we'll nearly always parse through the end of this document before running timeouts.
I didn't work in the onload handler, but I added a call to document.body.offsetLeft to force a layout. This allowed me to remove the waitUntilDone/notifyDone calls.
>> LayoutTests/fast/forms/slider-hit-testing.html:20
>> + var y = slider.offsetTop + (slider.clientHeight / 2);
>
> could you add some comments indicating what you are trying to click on here and what should be happening?
Done.